KR950007409B1 - A process to remove manganess dioxide use of hydrogen peroxide and of hydrogen peroxide and phosphonic acid - Google Patents

Abstract

No content.

Description

How to remove manganese dioxide from fiber using hydrogen peroxide and phosphonic acid

The present invention relates to a method of using hydrogen peroxide to remove dark manganese dioxide dye in a faded denim fabric or finished garment to provide a clear but faded appearance.

Denim garments such as jeans, jackets and skirts are recognized by the majority as more fashionable when they have a faded old look. Therefore, denim fabrics and / or garments are often bleached during the manufacturing process to give a bleached, excessively bleached, or blunt appearance. Such prebleached commodities are very marketable commodities, but they are relatively labor intensive for the commonly used bleaching process, which significantly increases the cost of the bleaching process.

U. S. Patent No. 4,218, 220 describes the production of uniformly faded denim garments, i.e., blue jean faded without stripes. To date, blue jean, satisfactorily fading without streaks, can only be obtained by repeated washing. The patent discloses, on denim fabrics, initial washing with detergents and emulsifiers, suitable intermediate rinsing operations, bleaching operations simultaneously acting bleach and quaternary ammonium fabric softeners, optionally adding the appropriate amount of detergent to the garment, further rinsing operations and / Or applying a wash cycle comprising any final treatment with a fabric softener and a laundry sour. The patent discloses the use of chlorine bleach, typically sodium hypochlorite, trichloroisocyanuric acid and the like.

U. S. Patent No. 4,852, 990 describes a method of modifying denim garments first and then contacting with an aqueous polyacrylic acid solution. Chlorine bleach is then added to give a uniformly bleached appearance.

Thereafter, there was a tendency to eliminate the uniform fading and to provide an apparently fading effect in appearance. One indication of this tendency is to implement rocking or stone-washing, i.e., spinning wet wet denim with pumice stones. The effect of this method is a used faded look with a natural fading, which is characterized by the contrast between the bright and dark areas, but in finished clothing the effect is likely to appear only around the seam, while the rest of the color remains almost uniform. Remains.

US Pat. No. 4,740,213 describes a method of impregnating particles of coarse porous material such as pumice with chlorine bleach and rotating drying in a drum with denim fabric. Subsequently, traces of chlorine bleach are removed, optionally by a burner such as acidic hydrogen peroxide.

However, chlorine bleach is known to damage cotton significantly, and as a result, alternative bleaches have been used to create fade look. Potassium permanganate is very preferred for such oxidative treatment. When applied in solution, they fade evenly; Impregnation with only inert porouss by locking results in the desired random heterogeneous oxidation of the chromosomes. Unfortunately, the deposition of dark insoluble manganese dioxide on denim results in a dull appearance. Manganese dioxide is prepared by a process called "neutralization", ie chemical reducing agents as described in US Pat. Nos. 4,795,476, 534,450, 1,361,833 and 3,384,444, usually sulfites, thiosulfates, hydroxylamines, and the like. Can be removed by reducing to soluble manganese salt. These reducing agents must be used in large amounts at pH 2.5 to 3.0 and damage cotton fibers. Excess reducing agent in the neutralization stage is very undesirable for disposal due to the very high toxicity and high chemical oxygen demand (COD) of the effluent.

After neutralization the denim is usually "whitened" or bleached to improve the contrast between the dyed and bleached areas. Hypochlorite bleach or sodium perborate bleach bath is usually used for brightening.

US Pat. No. 5,006,124 discloses contacting a washed fabric with potassium permanganate and subsequently neutralizing the discolored denim fabric between pH 3.0 to 6.0 in the presence of 1: 1 mole ratio of aminopolycarboxylic acid chelating agent (e.g. NTA) and hydrogen peroxide. A method of fading and bleaching denim fabrics is disclosed. The bleached denim fabric is subsequently bleached with an alkaline bleach solution of hydrogen peroxide.

This method is very effective. However, some bleach plants are limited in the equipment available and it is better not to require an alkaline bleaching step followed by a separate acid neutralization step. Another disadvantage is the cost of the chelating agent and ultimately its disposal.

Pending United States Patent Application No. 651,811, filed Feb. 7, 1991, wherein the oxidized denim fabric is contacted with an aqueous solution containing about 1.5 to 30 parts by weight of peracetic acid per 100 parts by weight of the denim fabric to neutralize the denim fabric. A process for processing denim bleached with potassium permanganate is disclosed. The aqueous solution also contains acetic acid and hydrogen peroxide sufficient to provide a weight ratio of 1: 1: 1.5 peracetic acid: acetic acid: hydrogen dioxide. Although the process is very effective, high concentrations of acetic acid (1.25-3.75 moles per mole of peracetic acid) are required. Such high concentrations of acid (less than pH 3.5) can degrade cotton fibers and neutralize acid spills prior to disposal.

The present invention wet-processes a denim fabric by the step of desizing the denim fabric, washing the desized fabric, and contacting the washed fabric with potassium permanganate to oxidize a portion of the color of the denim fabric to partially bleach the denim fabric. In the process, the bleached denim fabric is 0.5 to 5% owg hydrogen peroxide, about 1 to 3% owg C ₂ to C ₃ aliphatic carboxylic acid and about 1 to 2% owg phosphonic acid chelating agent based on the weight of the article Disadvantages of the prior art are presented by presenting a wetting process for denim fabrics characterized by removing manganese dioxide deposited on the discolored denim fabric by contacting with an aqueous solution of a pH of about 3.5 to 5 at a temperature of about 50 ° C to about 90 ° C. It can be overcome.

Denim fabrics can be processed in any conventional form, such as primitive products, partially woven or finished clothing. Denim is usually woven with dyed warp and white weft, but the term also includes striped denim fabric or denim fabric woven with both colored warp and weft yarns. Usually, denim is dyed with bat dyes such as indigo or sulfur dyes. Denim fabrics may also be woven into blend fabrics of cotton and synthetic fabrics.

The presence of aliphatic carboxylic acids is important in this process. The aliphatic carboxylic acid may be monocarboxylic acid or polycarboxylic acid, and may contain one hydroxyl group, preferably the carboxylic acid is acetic acid or citro acid. Preferably, the carboxylic acid is acetic acid. This acid can be added as a salt, as a free acid, or in any other convenient form.

pH can be adjusted by adding an inorganic acid or alkali metal hydroxide as needed. It is surprising that the process is effective in the range of pH 3.5-5. It is well known that cotton decomposes severely when the pH is lower than 3 or 3.5, and hydrogen peroxide not only oxidizes manganese ions to MnO ₂ in neutral solution, but also the newly precipitated brown dye of MnO ₂ is a violent decomposition catalyst for hydrogen peroxide. Known. According to US Pat. No. 4,552,675, hydrogen peroxide is known to dissociate into free radicals even when manganese forms chelates with coordination compounds.

The lower pH 3.5 of the present invention is important to avoid deterioration of cotton fabrics, and the upper limit of pH 5 is important to prevent redeposited manganese dioxide onto the fabric, and the preferred range of about pH 4 is to minimize the damage to the fabric. Provides good removal in a reasonable time (due to minimization of reprecipitation).

The temperature may vary over a wide range from about 50 ° C to about 90 ° C. At temperatures below 50 ° C., the process is too slow (more than 2 hours) to run commercially, whereas at temperatures above 90 ° C. the rate of decomposition of hydrogen peroxide is excessive. Preferably the temperature should be about 60-65 ° C. while providing a reasonably short contact time of 5-20 minutes. Usually, in order to reach the desired removal rate of dyeing, it is preferable to repeat the process one or more times.

The process decolorizes the denim fabric, washes the desized fabric and decolorizes the denim fabric by contacting the washed fabric with potassium permanganate to oxidize the dye chromophore or color portion of the denim fabric into a form that is easy to remove from the fabric surface. It is useful for the production of denim with a pattern that is randomly faded by a process which neutralizes the discolored denim fabric by removing the residue of potassium permanganate and oxidized chromosomes.

Denim fabrics have an effective amount of peroxygen compound and 0.2 to 3% owg of surfactant (preferably 1 to 2%) and a sufficient time (5 to 15 minutes, preferably at pH 7 to 12 (preferably 9 to 10)) Can be removed by contacting for 10 to 12 minutes) to substantially eliminate the size agent. An effective amount of the peroxygen compound for desizing is preferably 0.5 to 3% owg sodium persulfate or 2% to 6% owg hydrogen peroxide. The temperature should be maintained at about 55 ° C to about 70 ° C, preferably 65 ° C. This process has an offsetting BOD advantage over the enzymatic design process and does not release boron compounds into the environment because sodium perborate desizes in the process.

Sodium persulfate or hydrogen peroxide is particularly preferred for removing both starch and polyvinyl alcohol, two types of sizing agents commonly used in weaving denim. The denim fabric can then be bleached by conventional means to whiten the remaining fabric, preferably with alkaline hydrogen peroxide.

All percentages used herein are by weight and "owg" refers to the weight of the product.

In the Examples the above procedure was used to illustrate aspects of the invention.

Decolorization process

A 4 in ² desized sample (approximately 5 g) was placed in a 500 ml Erlenmeyer flask, and the preparation of the sample or simulation of the decolorization process was performed. 50 ml of a 2% KMnO ₄ solution was added to the flask and allowed to react at room temperature for 15 minutes. The KMnO ₄ solution was poured out and the denim samples were washed three times with 100 ml of deionized water.

In the neutralization step, 100 ml of a neutralizing solution (adjusted to pH 4 with NaOH or H ₂ SO ₄ ) was added to the flask. Next, the flask was stirred at room temperature for 10 minutes. The neutralization liquid was poured out and the neutralization treatment was repeated as before. Samples were washed three times with 100 ml each of deionized water. Manganese (MnO ₂ ) removal was assessed from a random rating of 10 (no reduction in color) to 1 (no perceptible residual MnO ₂ color).

The efficiency of neutralization was measured in comparison to a control sample (“STD”) using an N-carboxylic acid chelating agent, diethylenetriamine pentaacetic acid (DTPA), as taught in US Pat. No. 5,006,124.

Example 1

A series of formulations were prepared to evaluate the representative phosphonic acid chelating agent, diethylene triaminepenta (methylenephosphonic acid). The efficiency and composition of the neutralization formulations are shown in [Table 1].

In Table 1, samples D, E and F and K, L and M also represent controls used to determine the degree to which citric acid and DTMPA contributed to removing brown MnO ₂ staining.

As is apparent from Table 1, the phosphonic acid chelate blend is significantly more effective than the standard N-carboxylic acid chelating agent DTPA. Although samples L and M show that citric acid itself has a positive effect on the reduction of staining, it is particularly surprising that the known chelating agent citric acid itself is less effective than DTMPA and acetic acid.

Example 2

Similar to Example 1, another series of formulations were prepared and evaluated in place of 1-hydroxyethylidene-1,1-diphosphonic acid (HEDP). Conditions and results are shown in Table II below. HEDP was much better than the DTPA N-carboxylic acid chelator formulation used as standard. Stric acid also showed less effect with HEDP than acetic acid. Clearly, Examples 1 and 2 show a synergy between phosphonic acid and the claimed C ₂ -C ₃ carboxylic acid and hydrogen peroxide. Most surprising is that synergy is most pronounced in the case of acetic acid. This observation is not explained in terms of low concentration and pH range of the reactants.

TABLE 1

1.Contains 2% owg diethylenetriaminepentaacetic acid as standard

2. Chelating Agent Diethylenetriaminepenta (methylenephosphonic acid) -DTMPA

3. Grade 1 = brown does not discolor;

10 = fully brown

TABLE 2

1.Contains 2% owg diethylenetriaminepentaacetic acid as standard

2. HEDP = (1-hydroxyethylylene) diphosphonic acid

1-hydroxyyterylene-1,1-diphosphonic acid

3. Grade 1 = brown does not discolor;

10 = complete brown

Claims (14)

Desizing the denim fabric, washing the desized fabric, and contacting the washed fabric with potassium permanganate to oxidize the color part of the denim fabric into a form that is easily removed from the fabric surface, thereby partially decolorizing the denim fabric. In a method of wet weaving fabrics, the decolored denim fabric may be treated with 0.5% to 5% owg hydrogen peroxide, 1% to 3% owg C ₂ to C ₃ aliphatic carboxylic acid and 1% to 2% owg at pH 3.5-5. And removing manganese dioxide deposited on the bleached denim fabric by contacting with an aqueous solution of phosphonic acid chelating agent as an essential ingredient. The method of claim 1, wherein the chelating agent is diethylenetriaminepenta- (methylenephosphonic acid). The method of claim 1, wherein the chelating agent is 1-hydroxyethylidene-1,1-diphosphonic acid. The method of claim 1 wherein the pH is four. The method of claim 1 wherein said aliphatic carboxylic acid is acetic acid. The method of claim 2 wherein said aliphatic carboxylic acid is acetic acid. The method of claim 3 wherein said aliphatic carboxylic acid is acetic acid. The method of claim 4 wherein said aliphatic carboxylic acid is acetic acid. The method of claim 5 wherein said temperature is from 60 ° C. to 65 ° C. 7. The method of claim 1 wherein said aliphatic carboxylic acid is citric acid. The method of claim 2, wherein the aliphatic carboxylic acid is citric acid. The method of claim 3 wherein said aliphatic carboxylic acid is citric acid. The method of claim 4 wherein said aliphatic carboxylic acid is citric acid. The method of claim 10, wherein the temperature is from 60 ° C. to 65 ° C. 12.